Date of Award

6-30-2016

Document Type

Open Access Thesis

Department

Chemical Engineering

First Advisor

James A Ritter

Abstract

The adsorption reversibility of gasses that are typically found in flue gas for coal based power plants, such as SO2, NO2, and NO, onto 13X and 5A zeolites was presently investigated. The four individual gas mixtures containing these species consisted of 74 ppm NO (balance He), 74 ppm NO2 (balance He), 42 ppm SO2 (balance He), and 500 ppm SO2 (balance N2), which were also consistent with the values that are found in flue gas. Another gas, 15.03 mol% CO2 (balance N2), was also used in this work to evaluate the role of exposing SO2 to the zeolite on their adsorption behavior toward CO2. The study included single cycle thermogravimetric analyses (STGA) with all gas mixtures, multiple cycle thermogravimetric analyses (MTGA) with the mixture containing 500 ppm SO2, and consecutive CO2 breakthrough studies through an adsorption bed containing 1 to 1.5 g sample of zeolites before and after saturating the samples to 500 ppm of SO2. All runs were executed at 70 oC during exposure to SO2, NO2 and NO and CO2, while during regeneration with nitrogen, the role of temperature is also investigated when possible. The absolute pressure was kept at 1 atm. Results show that NO and NO2 showed limited, but very reversible, behavior toward to both 13X and 5A. In the case of SO2 however, the results show that SO2 has a very negative effect on 13X, adsorbing irreversibly. Nitrogen purge at temperatures of even 450 oC were not sufficient to remove and desorb the SO2 from the 13X. A completely different result was observed with the 5A, where SO2 did not display any observable irreversible adsorption upon it. A simple purge of nitrogen at 70 oC overnight was sufficient remove most of the SO2 from the 5A zeolite. These results conclusively show that 5A could be used as a good candidate for an effective guard layer to protect the better, 13X zeolite, placed downstream for CO2 capture.

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